ADDITION POLYMERS

1. ADDITION POLYMERS

2. ADDITION POLYMERS A A A A A A A A monomers polymer linear ethylene (ethene) polyethylene branched propylene (propene) polypropylene many (n) monomers n A (A)n polymer

3. PREPARATION OF ADDITION POLYMERS CATIONIC MECHANISM

4. POLYMERIZATION concentrated, smaller amount, not cold Polymerization polymer A cationic polymerization catalyst (Ziegler Catalyst) can be used instead of H2SO4.

5. CATIONIC MECHANISM could be as simple as a proton from sulfuric acid styrene + Catalyst resonance stabilized (Markovnikoff) H2SO4 or (+) (+) cationic catalyst (+) etc. Polystyrene

6. POLYSTYRENE n repeating unit

7. COPOLYMERS Polymers which are formed by combining two different monomers in alternating fashion are called copolymers. A B A B + + + A B A B butadiene styrene styrene-butadiene rubber (SBR)

8. THERMOPLASTICS Thermoplastics can be softened or melted by heat and reformed (molded) into another shape. Most addition polymers are thermoplastics. The polymer chains are held together by weak interactions (noncovalent bonds) such as : van der Waal’s forces, London dispersion forces and Dipole-dipole attractions. These interactions are disrupted by heating, allowing the chains to become independent of each other. Heating and reforming can be repeated indefinitely (if degradation doesn’t occur). This allows recycling.

9. PLASTICIZERS Most polymers of high molecular weight are quite rigid. These polymers can be softened and made flexible by adding plasticizers, usually dialkyl phthalate esters, such as dibutyl phthalate, a high boiling liquid. dibutyl phthalate The plasticizer separates the individual polymer chains from one another. It acts as a lubricant which reduces the attractions between the polymer chains.

10. THERMOSET PLASTICS Thermoset plastics melt initially, but on further heating they become permanently hardened. Once formed, thermoset plastics cannot be remolded, and they cannot be recycled. On heating, thermoset plastics become cross-linked (covalent bonds form between the chains). The cross-linked chains form a rigid network heat linear cross-linked

11. HIGH-DENSITY POLYMERS Linear polymers with chains that can pack closely together. These polymers are often quite rigid. LOW-DENSITY POLYMERS Branched-chain polymers that cannot pack together as closely. There is often a degree of cross-linking. These polymers are often more flexible than high- density polymers.

12. SOME COMMON ADDITION POLYMERS uses example monomer polymer most common polymer bags, wire insulation, squeeze bottles polyethylene polypropylene fibers, bottles, indoor-outdoor carpet polystyrene styrofoam, inexpensive molded objects: household items, toys synthetic leather, clear bottles, floor coverings, water pipe polyvinyl chloride (PVC) non-stick surfaces, chemically resistant items Teflon polyacrylonitrile fiber used in sweaters, blankets, carpets (Orlon, Acrilan)

13. COMMON ADDITION POLYMERS (cont) uses example monomer polymer poly(methyl methacrylate) unbreakable glass, latex paint (Lucite, Plexiglass) adhesives, latex paints, textile coatings chewing gum poly(vinyl acetate) (PVA) natural rubber the polymer is cross- linked with sulfur (vulcanization) neoprene rubber cross-linked with ZnO, resistant to gasoline and oil

14. PREPARATION OF ADDITION POLYMERS CATIONIC AND FREE-RADICAL PROCEDURES MECHANISMS

15. CATIONIC MECHANISM could be as simple as a proton from sulfuric acid styrene + Catalyst resonance stabilized (Markovnikoff) H2SO4 or (+) (+) cationic catalyst (+) etc. Polystyrene

16. R-O-O-R . 2 R-O RADICAL MECHANISM styrene . . Catalyst resonance stabilized (.) (.) Catalyst (.) . . etc. Polystyrene

17. ZIEGLER-NATTA CATALYSTS POLYMERIZATION

18. Ziegler-Natta Catalysts Cationic, anionic or radical processes are not involved and the polymerization is often stereoselective (next slide). + potential coordination site fo alkene insertion etc.

19. STEREOISOMERIC POLYPROPYLENE POLYMERS stereoregular polymers ISOTACTIC all methyl groups on the same side SYNDIOTACTIC methyl groups alternate sides not regular ATACTIC methyl groups randomly oreinted

20. CONDENSATION POLYMERS A DIFFERENT TYPE OF POLYMER NOT AN ADDITION POLYMER !

21. CONDENSATION POLYMERS Condensation polymers are copolymers made from more than one type of monomer. Many functional groups are used (instead of alkenes) and each type of monomer has a different functional group. When condensation polymers are formed, a small molecule (usually H2O) is often eliminated as each bond forms. Ethylene glycol Terephthalic acid Dacron polymer

22. SOME COMMON CONDENSATION POLYMERS

23. RECYCLING CODES

24. CODE SYSTEM FOR PLASTIC MATERIALS These codes allow consumers to separate plastics for recycling. polyethylene terephthalate soft drink bottles PETE 1 milk and beverage containers, products in squeeze bottles high-density polyethylene HDPE 2 polyvinyl chloride bottles with cleaning agents in them, some shampoo bottles 3 V thin plastic bags, plastic wrap low-density polyethylene LDPE 4

25. PLASTIC MATERIALS CODE SYSTEM (cont) 5 PP polypropylene heavy-duty, microwavable containers used in the kitchen PS 6 polystyrene foam beverage cups, envelope windows 7 Other All other resins, multilayered materials, containers made of other materials ketchup bottles, snack containers, mixtures where the top differs from the bottom The codes are frequently stamped on the bottom of containers.